1. Field of the Invention
The present invention relates to an image processing apparatus and, more particularly, to an image processing apparatus which applies various special effects to, for example, an NTSC or PAL system television signal.
2. Description of Related Art
An image processing apparatus which realizes various special effects by using a field memory has heretofore been proposed. For example, the field memory is used for realizing special effects such as a still image display (a freeze effect), a stroboscopic effect, an electronic zoom effect which enlarges and displays a portion of an image, and a field-cyclic noise reducer.
Among these special effects, the still image display using a video signal for one field involves a large degradation of image quality, and various methods of improving the image quality of the still image display have heretofore been proposed.
(1) There is a method of writing the video signal of an input moving image into a frame memory and, after that, reading the video signal from the frame memory for displaying purpose. In this method, since no vertical resolution degradation occurs in a portion in which a subject is stationary, a degradation in image quality does not occur. However, since the required memory capacity is twice as large as the capacity of a field memory, there is a problem such as an increase in cost.
(2) There is a method using a field memory. For example, during reading, a signal is read without modification in the case of an odd field, whereas an interpolation signal is generated from the signals on adjacent horizontal lines in the case of an even field and the interpolation signal is outputted. In this method, although there is no image shake due to a motion between fields, a vertical resolution is degraded and the resultant image quality is inferior to the image quality of an apparatus using a frame memory.
The still image display method for the conventional image processing apparatus has a number of problems. In the case of an apparatus using a field memory, a vertical resolution is degraded, so that image quality is degraded. If a frame memory is used for improving image quality, two field memories are needed, so that the problem of a cost increase occurs.
In the light of the above-described background, an object of the present invention is to provide an image processing apparatus and an image processing method both of which can realize special effects such as still image display of high quality and enlarged display without the need to increase the required memory capacity.
To achieve the above object, in accordance with one aspect of the present invention, there is provided an image processing apparatus which comprises first input means for inputting a video signal, second input means for inputting a control signal indicative of a special effect mode to be applied to the video signal, compressing means for compressing the video signal inputted by the first input means, memory means for storing the video signal, and memory control means for, according to the control signal, causing the memory means to selectively store the video signal compressed by the compressing means and a video signal not compressed by the compressing means.
In accordance with another aspect of the present invention, there is provided an image processing method for applying a special effect to a video signal by using a memory, which method comprises a first input step of inputting the video signal, a second input step of inputting a control signal indicative of a special effect mode to be applied to the video signal, a compressing step of compressing the input video signal, and a memory control step of, according to the control signal, causing the memory to selectively store the video signal compressed in the compressing step and a video signal not compressed in the compressing step.